Alloy



H. WINTER Nov. 19, .1968

ALLOY 3 Sheets-Sheet 1 Filed Feb. 8, 1965 nz w im t CL 422 202 322-202- E 32: .(nT 22 I 61.76 222 n? B N A2! I NT F1 Nov. 19, 1968 Filed Feb. 8, 1965 FIG.3

HARDNESS, Kp/rnm H; III/INTER 3,411,901

ALLOY 3 Sheets-Sheet 2 300 O HV 3O I 0 Hv30AFTER- -I-IRHEATING AT 800C 0 NV 5 AT 800C 0 200 %A!+ Nb BY WEIGHT HARDNBS TO ROOM AND ELEVATED TEMPERAIU OF ALLOYS ON SECTION Ti-NbAl As A FUNCTION OF THE AI +Nb CONTENT BY WEIGHT FIG. 2

300 o HV3O 0 Hv AFTER' HR HEATING AT800c 0 W5 AT 800C 9. Al Nb BY WEIGHT I-IARDNESS TO ROOM AND ELEVATED TEMPERATURES OFALLQYS ON SECTION TI-NbAl WITH AN ADDITION CFO-5 A BY WEIGHT OF Si AS A FUNCTION OFTHE AI +NbCONTENT BY WEIGHT.

H. WINTER Nov. 19, 1968 ALLOY 3 Sheets-Sheet 5 Filed Feb. 8, 1965 00m 00m 8* 00m 00m x HwNaai 3119131 United States Patent 3,411,901 ALLOY Heinrich Winter, Eschborn, Taunus, Germany, assignor to the Federal Republic of Germany as represented by the Secretary of Defense Filed Feb. 8, 1965, Ser. No. 430,794

Claims priority, application Germany, Feb. 15, 1964,

2 Claims. (Cl. 75-1755) ABSTRACT OF THE DISCLOSURE Ternary titanium base alloys of improved high temperature strength contain about 15.5 percent of aluminum, about 18 percent of niobium and about 0.5 percent of S1.

This invention relates to novel titanium base alloys and more particularly to ternary titanium base alloys containing aluminum and niobium which are forgeable and possess high oxidation resistance and strength at elevated temperatures.

As titanium base alloys having favorable high temperature properties, the so-called super a alloys such as Ti-7Al-12Zr and Ti-8Al-2Nb-1Ta are known. They have good strength properties up to temperatures of about 600 C. and good oxidation resistance.

Recently, alloys of the composition Ti-Al-Nb containing 10 to percent of aluminum have become known, some of which can be used up to 1000 C. and are forgeable in air at about 1200 C.

I have now found that such Ti-Al-Nb alloys containing 10 to 30, preferably about 12 to 17 percent by weight of Al, wherein the ratio of Al:Nb is about 7:8, possess particularly excellent high strength properties at elevated temperatures.

Addition of silicon up to 2%, particularly in the range of 0.25 to 1.25 percent by weight, improve the workability as well as the high temperature strength and oxidation resistance of the alloys. The greatest influence of an Si addition was found on the 100 hour-rupture strength. An addition of 0.5% Si increased said strengths in the alloy Ti-15.5Al-18Nb at 800 C. and 100 hours to 17 kp./mm.

The values of the strength properties of the improved alloys as a function of their composition are illustrated in the drawings, in which FIG. 1 shows the position of the novel alloys in the Ti-Al-Nb diagram;

FIG. 2 shows the hardness data at room temperature and elevated temperatures as a function of the Al-i-Nb content of the alloys;

FIG. 3 is similar to FIG. 2, showing the influence of a 0.5% Si addition to the alloys, and

FIG. 4 shows the temperature dependence of the tensile strength of my novel alloys in comparison to known titanium alloys.

The diagram of FIG. 1 shows that the alloys of this invention are all located on a section of the Ti-Al-Nb ice diagram passing through a point corresponding to the composition TiNbAl As shown by the graphs of FIGS. 2-4, an alloy containing 15.5% Al and 18% Nb presents optimum characteristics of hardness and tensile strength at high temperatures of about 800 C. For instance, the tensile strength of such alloys as cast was found to be 57 kp./mm. at 800 C. and 47 kp./mm. at 871 C. (see FIG. 4). Compared with the data of prior art titanium alloys, said values are quite exceptional.

The HV ordinates in the drawings designate the Vickers hardness, whereby the numerical values refer to the load in kg. applied for the tests, in accordance with the ofiicial German testing standards, published as DIN 50133.

Elongation tests of the novel alloys show at 800 C. an elongation of about 5 to 15%.

The conversion factor between the hardness of 800 C., which was determined by a Vickers diamond, and the tensile strength o'B at 800 C. was determined as =O.25. The tensile strength at said temperature is, therefore, about A of the value of the hardness.

The alloys of the invention are of the alpha-beta type. In addition, they may contain small amounts of Hf, Zr, or Sn (about 1%) which may improve further the workability and high temperature strength.

In alloys which contained a relatively low content of aluminum and niobium, the low and high temperature strength characteristics can be improved by addition of tin in amounts of 3 to 5 percent.

All percentages given herein are percentages by weight.

I claim:

1. A forgeable titanium base alloy having good high temperature properties and oxidation resistance consisting of about 15.5 percent of aluminum, about 18 percent of niobium, about 0.5 percent of silicon and the balance titanium with incidental impurities.

2. An alloy as claimed in claim 1 containing, in addition, at least one member of the group consisting of hafnium, zirconium, and tin, said hafnium and zirconium being present each in an amount up to 3 percent, the tin in an amount up to 5 percent.

References Cited UNITED STATES PATENTS 2,754,204 7/1956 Jafl'ee et al -1755 2,880,088 3/1959 Jafi'ee et al 75175.5 2,940,845 6/1960 Jaffee et a1 75-175.5 X 3,008,823 11/1961 McAndrew 75-1755 2,893,864 7/1959 Harris et al 75-175.5 2,918,367 12/1959 Crossley et al. 75l75.5

FOREIGN PATENTS 782,564 9/ 1957 Great Britain.

OTHER REFERENCES OTS 62-587 release, Development of Ti-Al-Nb Alloy for Use at 1200-1800 F. March 1962.

CHARLES N. LOVELL, Primary Examiner. 

